Pbx toll connector providing special service



Aug. 21, 1962 c. E. LOMAX PBX TOLL CONNECTOR PROVIDING SPECIAL SERVICE 2Sheets-Sheet 1 mzI Filed Dec. 8, 1958 mmohomzzoo mmIhO O.

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INVENTOR. CLARENCE E. MAX 56?- ATTY.

2 Sheets-Sheet 2 n a v u 1 m; m

C. E. LOMAX 5 all 3" PBX TOLL CONNECTOR PROVIDING SPECIAL SERVICE Aug.21, 1962 Filed Dec.

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CLARENCE E. LOMAX ATTY.

United States Patent @fiiice 3,650,590 Patented Aug. 21, 1962 ware FiledDec. 8, 1958, Ser. No. 778,810 6 Claims. (Cl. 179-27) The presentinvention relates to telephone systems in general, but more particularlyto such systems employing the use of PBX toll connectors providingcertain special services.

It is a primary object of the present invention to provide a PBX tollconnector incorporating new and improved circuit arrangements, wherebythis connector will extend a toll connection to a selected PBX in anefiicient and reliable manner with a minimum consumption of time whentaken into use by a toll operator.

Another object of the present invention is the provision of a partialrelease or modified, camping service by the improved PBX toll connector.

In accordance with the above-mentioned objects, a feature of theinvention relates to the inclusion of means in the toll connector forreleasing only this connector in the switch train in the event that aPBX trunk group, or single trunk PBX, is called and found busy.

Another feature of the invention relates to means for maintaining thereleased toll connector in a partial release camping condition while thepreceding switches in the switch train are maintained in the operatedcondition.

Another feature of the invention relates to means in the toll connectorcontrolled by the toll operator for operating the connector from itspartial release camping condition to retest the same PBX trunk group, orsingle trunk PBX, for an idle trunk.

Still another feature of the invention relates to means in the tollconnector for returning busy tone to the toll operator after theconnector has released and is in its partial release clamping condition.

A further feature of the invention relates to the toll connector beingreoperated to test the busy PBX trunk group, or PBX trunk, responsive tothe toll operator dialing only the last two digits of the call number.

Another feature of the invention relates to an arrangement of theabove-mentioned features in connection with a plurality of the improvedtoll connectors, wherein each of the connectors will restore to apartial release clamping condition responsive to a PBX trunk group, orPBX trunk, being tested and found busy. All the connectors may bereoperated responsive to the dialing of the last tWo digits of the callnumber and the first connector to connect with the idle PBX trunk group,or PBX trunk, will switch through and busy these trunks to the otherconnector to cause them to restore to the partial release campingconditions.

Another feature of the invention relates to the connector release relayin the toll connector, and means for holding the release relay operatedby ground over the toll C conductor from the preceding switches.

These and other objects and features of the invention will becomeapparent upon a further perusal of the specification and claims taken inconjunction with the acompanying drawings comprising FIGS. 1 and 2.which shows by means of the usual diagrams a sufiicient amount of theapparatus to enable the invention to be described and understood and inwhich:

The left-hand side of FIG. 1 discloses block diagrams representing thepreceding switching elements of a toll switch train, with respect to thetoll connector. The right-hand side of FIG. 1 discloses in schematicform,

a portion of the improved circuit representing the PBX toll connector.

The left-hand side of FIG. 2 discloses in schematic form, the remainingportion of the improved circuit representing the PBX toll connector. Theright-hand side of FIG. 2 discloses the toll connector contact bank withtrunks of various PBX groups connected thereto for extending connectionsto a plurality of PBX switchboards.

ln order to more clearly understand the illustrated application of theinvention, it is though advisable to point out that the drawings shouldbe arranged so that the conductors on the left-hand of FIG. 2 will bealigned opposite the like-numbered conductors on the righthand side ofFIG. 1.

It is further thought advisable to point out that While the instantdisclosure shows a PBX toll connector as being included in a toll switchtrain that is relatively simple, this connector may also be included ina much more complex toll switch train, wherein the services offered bythis connector are required.

In its preferred form, such as disclosed in the present application, abrief description of the invention will hereafter be given.

BRIEF DESCRIPTION The toll dial trunks are taken into use in a wellknownmanner responsive to the toll operator initiating a call, while the tolltransmission selector also operates in a well-known manner responsive tothe toll operator dialing the preliminary digits of the call number ofthe desired PBX trunk, or group. The toll transmission selector isthereby operated to search for an idle PBX toll connector. The idlecondition of a PBX toll connector is indicated by the presence ofbattery on the toll C conductor, which is applied thereto through thelower winding of the changeover relay such as 140. At the time that thetoll C Wiper of the toll transmission selector encounters this batterypotential on the toll C conductor of an idle toll connector, a circuitis completed for operating the stop relay (not shown) in the tollselector, whereby the selector stops hunting and switches through toseize the idle toll connector in a Well-known manner.

The toll operator then dials the remaining digits of the call number ofthe desired PBX trunk or PBX group, to operate the toll connector toestablish a signaling connection therewith. If the desired trunk or atrunk in the group is idle, the connector operates to complete thesignaling connection and subsequently completes the talking connectionin response to the answering of the call by the called party. In theevent that the trunk is busy, or all trunks in the group are found busy,the toll connector restores its wipers to normal and busy tone is sentto the operator, while at the same time the preceding switches do notrelease. If desired, the toll operator can leave the connection set upin this busy condition, handle other calls, and then return to the busyconnection and redial the last two digits of the call number, with tollconnector switching through if the trunk or a trunk in the group isfound idle, and again restoring its wipers to send busy tone to theoperator if they still test busy. The operator may repeatedly make thesetests by redialing the last two digits of the call number until thecalled trunk or a trunk in the called group is found idle, therebysaving effort and time and also providing the thandling of simultaneouscalls to the same busy trunk or trunk group.

A detailed description of the invention including the previouslydescribed permanent features and the operations involved in setting upconnections in a system embodying the same will now be given, referencebeing had in particular to FIGS. 1 and 2.

DETAILED DESCRIPTION PBX Call With First Trunk of Group Being Idle Itwifll be assumed that the toll operator at the toll board has been askedto extend a connection to the PBX such as 01, and that a group of tentrunks are accessible from the tenth level of the toll connector to thisparticular PBX. Responsive to the operator initiating the call, the tolldial trunk and the toll transmission selector are taken into use in aWell-known manner. The toll transmission selector also operates in awellknown manner responsive to the operator dialing the preliminarydigits of the particular call number, whereby the selector hunts for anidle PBX toll connector.

It is further assumed that the toll transmission selector is a batterysearching selector of the well-known type, and that an idle PBX tollconnector indicates such condition by placing battery potential on thetoll C conductor. It is also assumed that the PBX toll connectordisclosed in FIGS. 1 and 2 is the first idle connector encountered bythe toll selector. Therefore, when the toll C wiper of the toll selectorencounters this abovementioned battery potential on the toll C conductorof the illustrated connector, a series circuit is completed foroperating the stop relay (not shown) in the selector and for operatingthe changeover relay such as I49 in the connector. This circuit may betraced as extending from ground (not shown) in the selector, through theselector stop relay (not shown), the selector toll C wiper, the toll Cconductor engaged by the toll C wiper, contacts 133 and through thelower Winding of chan eover relay 14 d to battery.

The resulting subsequent operations of the toll selector are well-knownand essentially briefly entails the operation of the stop relay (notshown) for preventing further hunting and stopping the selector wiperson the bank contacts terminating the conductors of the idle tollconnector and the operation of the selector switching relay (not shown)for extending the closed loop circuit into the toll connector tocomplete a circuit for operating the connector line relay 11%. Thiscircuit for line relay 110 may be traced as extending from groundthrough the lower winding of line relay 110, contacts 103, the |-L lineconductor engaged by the +L wiper of the toll transmission selector,over the closed loop, the '-L wiper of the toll transmission selectorand the engaged L line conductor, contacts wt and through the upperwinding of line relay 110 to battery.

Changeover relay 140 operates over the above-traced circuit before linerelay Illtl operates, and in actuating its contacts 141 prepares a pointin the operating circuit for relay 130, at contacts 142 prepares both apoint in the holding circuit for itself and a point in the pulsingcircuit to vertical magnet I60 and at contacts 143' opens a point in thepulsing circuit to rotary magnet 270.

In actuating its contacts, line relay lit? completes an obvious circuitat contacts 111 for operating release relay 129 and opens a point atcontacts 112 in the pulsing circuit.

In actuating its contacts, release relay I24) applies a control groundat contacts 121 for operating relay 313% over an obvious circuit and foradditional use by the connector, prepares a point at contacts 122 in afuture looking circuit for the switching relay 230, locks itselfoperated at contacts 123 to the ground toll C conductor, prepares apoint at contacts 124 in the pulsing circuit and opens a point atcontacts 125 in the release circuit of release magnet 2 80.

In actuating its contacts, relay 130 completes an obvious shuntingcircuit at contacts 131 for relay 214), shifts the previously describedoperating circuit of changeover relay 140 at contacts 132 from thegrounded toll C condoctor and contacts 136 to a new circuit, whichprovides ground by way of the vertical otf-norrnal (VON) spring contact6, prepares a point in the circuit at contacts 134 for the releasemagnet 230 and completes an obvious circuit at contacts 135 foroperating ring cut-off relay This circuit for ring cut-off relay 150 maybe traced from ground potential (not shown), applied by the tolloperator in any well-known manner and forwarded over the EC conductor,contacts 105, 135 and through the lower winding of relay 150 to battery.Relay 150 is constructed as being slow-to-operate and will do so after apredetermined period of time.

In actuating its contacts, ring cut-off relay 150 completes its ownlocking circuit by way of contacts 156 to the grounded EC conductor, atcontacts 15-1 and 154 prevents the application of ringing current to theconnection for the present and performs no useful function for the timebeing at contacts 152 and 155.

The toll connector is now in condition to receive the last two dialeddigits of the call number, which for the purpose of the presentdescription shall be assumed to be the digits ()1 and represents thegroup call number.

Line relay 110 responds responsive to the dialing of the digit 0 andrestores and operates a total of ten times each, during which timevertical magnet receives ten pulses of ground potential over an obviouscircuit by way of contacts 112 to vertically step the connector wipers290 through 293 in a Well-known manner to the tenth, or 0 level. It willbe noted that each time that contacts 111 are opened, release relay 120is not affected, since it is locked operated to the toll C conductor byway of its own contacts 123'.

At the time that the connector wipers take their first vertical step,the VON spring contact 6 opens and VON spring contact 5 closes, therebycompleting an obvious holding circuit for relay 134] and opening thepreviously described holding circuit for changeover relay 140. However,since changeover relay 140 is constructed as being slow-to-release, itis held operated by the pulses from contacts 112 of line relay 110during the remainder of the vertical pulsing.

At the end of the vertical pulsing, changeover relay 140 is no longerheld operated and therefore restores before the last digit of the callnumber is dialed. In restoring its contacts, changeover relay 140 opensthe previously traced operating circuit of relay 130 at contacts 141,opens both the pulsing circuit to vertical magnet 160 and the pulseholding circuit to itself at contacts 142 and prepares a point in thepulsing circuit to rotary magnet 27% at contacts 143. It will beremembered that relay 130 is now held operated to ground by way of VONspring contact 5.

The toll connector is now in condition to receive dial pulsesrepresenting the last digit 1 of the group call number. Line relay 119responds responsive to the digit 1 being dialed and restores andoperates a total of one time each, during which time rotary magnet 270receives one pulse of ground potential, by way of contacts 112 of linerelay 110, to horizontally step, or rotate, the connector Wipers 290through 293 in a wellknown manner to engage the first bank contacts ofthe tenth level. This pulse of ground potential also completes a circuitfor operating relay 240 in series with rotary magnet 270 and furthercompletes a circuit for preenergizing relay 259 so that it will operateas soon as relay 240 operates. The series circuit for relay 240 androtary magnet 270 may be traced as extending from ground, contacts 112,124, 143, conductor 17, contacts 225, 236, the winding of relay 240 andthrough the winding of rotary magnet 270 to battery. The circuit forpreenergizing relay 250 may be traced as extending over the first partof the abovetraced circuit, through the winding of relay 240, contacts242 and through the winding of relay 250 to battery.

In actuating its contacts, relay 240 completes the operating circuit atcontacts 241 for the preenergized relay 250, opens the previously tracedpreenergizing circuit at contacts 242, prepares both an alternate pointat contacts 243 in the pusing circuit to rotary magnet 270 and in thepulse holding circuit for itself and opens a point at contacts 244 inthe energizing circuit to the rotary step relay 260.

In actuating its contacts, relay 250 opens a point at contacts 251 inthe busy tone circuit, removes an operating ground at contacts 252 fromthe present incomplete circuits of relays 290 and 210, opens a point atcontracts 253 in the operating circuit of switching relay 230, completesthe busy test circuit at contacts 254 to the busy relay 220, opens apoint at contacts 255 in the locking circuit of busy relay 220 andprepares a point at contacts 256 in the energizing circuit of relay 260.

At this point in the operational description, it will be summarized thatthe dialing of the last digit 1 of the call number has ceased, wipers290 through 293 are engaged with the first bank contact in the tenthlevel terminating the first trunk of the trunk group, the pulse holdingcircuit to relay 240 is no longer effective and this slow-to-releaserelay is now in the process of releasing and a busy test has just beeninitiated of this first trunk in the trunk group assigned to the PBX()1.

Relay 240 restores before the busy test is efiective and opens thepreviously mentioned operating circuit of relay 250 at contacts 241,prepares an alternate holding circuit at contacts 242 for relay 250 inthe event that this particular first trunk of PBX 01 should test busy,opens the previously mentioned alternate point in the pulsing circuit atcontacts 243 and closes the previously mentioned point in the circuit tothe rotary step relay 260 at contacts 244.

It will be assumed, as previously mentioned, that there are a total often PBX trunks in the trunk group assigned to PBX 01 and that each ofthem terminate at a different bank contact in the tenth level. It willalso be noted that while it is not shown, all the C and EC bank contactsof each trunk but the last one in each group are connected, or strapped,together in a wellknown manner, whereby the busying ground normallyapplied to the C conductor is also sent out over the EC conductor toprovide means in order for the toll connector to automatically trunkhunt until an idle trunk is found, or until all trunks have been testedand an alltrunk busy condition exists, as will be explained in detaillater on in the specification.

For this part of the description it will be assumed that the first trunkconnected to the first set of bank contacts assigned to PBX 01 is idle,the connector will operate as hereafter described.

Since this first trunk in the group of PBX ()l is idle, as mentionedabove, there will be no busying ground on its C and EC conductorsconnected to the respective bank contacts, which are engaged by theconnector C and EC wipers 292 and 293 respectively. Battery (not shown),which is indicative of the idle condition of the trunk, is connected tothe C conductor in any well-known manner or method. This batterypotential is encountered by C wiper 222 and EC wiper 293 of theconnector with no apparent effect on the connector for the present untilslow-to-release relay 250, which is not held operated, has had time torestore.

Upon its release, relay 259 closes a point in the busy tone circuit atcontacts 251, prepares a point in the circuits to relays 200 and 210 atcontacts 252, completes the circuit at contacts 253 for operatingswitching relay 230, opens a point at contacts 254 in the busy testcircuit to busy relay 220, prepares a point at contacts 255 in thelocking circuit to busy relay 220 and opens a point at contacts 256 inthe circuit to the automatic rotary stepping relay 260. The circuit foroperating switching relay 230 may be traced as extending from ground atcontacts 121, conductor 15, contacts 223, the upper winding of switchingrelay 230, contacts 253, C wiper 292 and engaged bank contact to theabove-mentioned bat tery in the seized trunk.

In actuating its contacts, switching relay 230 completes its own lockingcircuit for an obvious path at X contacts 235, prepares a point atcontacts 231 in the ringback tone circuit, prepares points at contacts23-2 and 233 in the extension of the talking conductors to the trunk,applies both a holding and busying ground for the trunk and completes ashorting circuit for its upper winding at contacts 234, opens thepulsing circuit to relay 240 and rotary magnet 270 at contacts 236,opens a point in the circuit to the release magnet 280, closes analternate holding circuit at contacts 238 to the ring cut-elf relay 150and at contacts 239 completes an obvious circuit from the grounded tollC conductor to operate relay 1%.

In actuating its contacts, relay disconnects line relay 110 from thepreviously mentioned closed loop circuit at contacts 101 and 103, closespoints at contacts 192 and 104 for extending the talking connectionthrough to the connector wipers, opens the previously traced operatingcircuit at contacts 105 to ring cut-off relay 150 and opens thepreviously mentioned alternate holding circuit at contacts 106 to thering cut-ofl' relay 150. Ring cut-off relay 150 is still held operatedby way of its X contacts 156 to the grounded EC conductor. The removalof line relay 110 from the loop circuit causes the operator to benotified or signaled in a well-known manner to inform her that she hasline seizure supervision and that she may thereafter initiate theapplication of ringing current to the connection. The release of linerelay 110 and the closing of its contacts 111 and the opening of itscontacts 112 have no effect on the connector during the remainder of thedescription.

In order to initiate ringing, the operator momentarily removes thepreviously mentioned ground potential from the EC conductor, whichthereby allows ring cut-off relay 159 to restore.

In restoring its contacts, ring cut-ofi? relay 150 applies ringingcurrent at contacts 151 and 154 to the line conductors of the calledtrunk line in a well-known manner to sigal the operator at the PBX 01,opens the conductors of the talking connection at contacts 152 and 155for the time being, completes an obvious circuit at contacts 153 for theapplication of ringback tone to the L line conductor leading to thepreceding switches to inform the calling operator that a signalingconnection has been established and opens its previously describedholding circuit at X contacts 156.

After a reasonable length of time the call is answered at PBX O1 andring cut-off relay 150 is operated responsive to the answering in aWell-known manner. In actuating its contacts, relay 150 completes itspreviously traced locking circuit to the EC conductor at X contacts 156,

removes the application of ringing current over the called trunk line atcontacts 151 and 154, opens the ringback tone circuit to the L lineconductor leading to the calling operator at contacts 153 and completesthe talking connection by closing contacts 152 and 155. The tolloperator has answering supervision, due to the closed loop of the calledtrunk being extended through the connector to the preceding equipment.

The preceding equipment is arranged in a well-known manner to preventthe release of the connection while the called party is still on theline. However, at the end of conversation and responsive to the calledparty hanging up, the toll operator can release the connection byremoving the forwarding grounds from the EC conductor and from the tollC conductor. Relay 11M and release relay restore due to the ground beingremoved from the toll C conductor, with ring cut-off relay starting torelease but then being held temporarily by contacts 106 of relay 100,since relay 100 restores at once.

In restoring, release relay 12G removes the operating ground from theconnector to restore switching relay 230 and prepares a point in theoperating circuit at contacts 125 to the release magnet 280.

Switching relay 230 now restores and at contacts 237 opens theabove-mentioned holding circuit to the ring cut-off relay 150 andcompletes the circuit to the release magnet 280 at contacts 237. Thiscircuit for release magnet 280 may be traced as extending from ground,contacts 112, 125, 13 conductor 18, contacts 237 and through the windingof release magnet 280 to battery. Relay 150 restores at this time.

Release magnet 280' operates to restore the connector wipers to theirnormal position in a well-known manner, at which time VON springs 5 opento remove the locking circuit from relay 130. Relay 130 thereafterrestores to return the connector to its normal unoperated condition.

The equipment is now at normal and conditioned to handle future calls.

Automatic Trunk Hunting With First Trunks of PBX Group Being Busy Adescription will now be given wherein it is assumed that the first trunkand an undetermined number of subsequent trunks in the trunk groupassigned to PBX 01 are busy and that automatic trunk hunting takes Placein response to these trunks being individually tested in succession andfound busy.

In describing the operation of the connector during this type of call,it will be pointed out that the same operations take place as describedin the previous section, wherein the call was initiated, the tollconnector Was seized and the last two digits ()1 of the call number weredialed to operate the connector to engage its wipers with the first setof bank contacts in the tenth, or 0, level. As previously mentioned,this first set of bank contacts in the 0 level are connected with thefirst trunk in the trunk group that is assigned to PBX 01. Also aspreviously mentioned, it will be again .pointed out that there are tentrunks as signed to this particular PBX and that the C and EC bankcontacts corresponding to all trunks but the last one in the group areindividually connected, or strapped, in order to provide the automaticrotary trunk hunting which will hereafter be described.

It is therefore assumed that the last digit 1 of the call number hasbeen dialed and the connector has rotated its wipers 290 through 293into engagement with the first set of bank contacts representing thefirst trunk of the PBX group in the tenth level and a busy test of thistrunk is made.

Since it has been stated that this first trunk is assumed to be busy anddue to the previously mentioned strapping arrangement, the busyingground normally encountered by the C wiper 25 2, is also encountered bythe EC wiper 293.

At this point in the description, it is pointed out that relay 250 hasoperated to cause the various conditions in the connector circuitry aspreviously described and the pulse holding circuit in ineffective forholding slow-to release relay 240 operated. However, before relay 240has had time to release, the busying ground potential encountered by theC wiper 292 completes an obvious circuit for operating busy relay 220.

In actuating its contacts, busy relay 220 prepares a point in the busytone circuit at contacts 221, prepares a point at contacts 222 in thecircuit to both shunt relay 21d and operate the release control relay260, opens a point in the energizing circuit of switching relay 230 atcontacts 223, prepares a point in the locking circuit to itself atcontacts 224, opens a point in the rotary dialing circuit at contacts225 and prepares a point in the circuit to the rotary step relay 260 atcontacts 226.

Slow-to-release relay 240 restores at this time and opens the energizingcircuit to the slow-to-release relay 250 at contacts 241, prepares apoint in the holding circuit to relay 250 at contacts 242 opens amultiple point in the rotary dialing circuit at contacts 243 andcompletes a circuit for energizing the rotary step relay 260 at contacts244. Relay 250 does not release for the present, since it is constructedas being slow-to-release. The circuit for relay 26%) may be traced fromthe ground (not shown) encountered by the EC wiper 293, contacts 226,244, 256, 262, 271, and through the winding of relay 260' to battery.

In actuating its contacts, relay 260 completes obvious circuits atcontacts 261 for holding relay 250 operated and for operating rotarymagnet 270 and completes a locking circuit for itself at contacts 262.This locking circuit for relay 26% may be traced as extending fromground at contacts 121, conductor 15, down through contacts 262, 271 andthrough the winding of relay 260 to battery.

Upon energization, rotary magnet 270 first steps the connector wipers29-5) through 293 to the next successive set of bank contacts and towardthe end of its operative movement opens the previously traced circuit torelay 26% at interrupter contacts 271. In this manner, relay 25s is heldoperated over its locking circuit until the Wipers have engaged the newset of bank contacts. In restoring, relay 260 opens the circuits torelay 250, rotary magnet 270 and the locking circuit for itself.

' However, relay 254) remains operated due to its slowto-rele-asecharacteristics and only rotary magnet 270 restores. It should be notedthat the circuit to the busy relay 221) will be momentarily openedduring the time that the C wiper 292 is leaving the C bank contact ofthe first busy trunk and engaging the C bank contact of the next trunk.However, since the next, or second, trunk is assumed to be busy, busyrelay 220 will remain operated from the ground encountered by the Cwiper 292 on the C bank contact of this second trunk over a circuit suchas previously traced. Therefore, when rotary magnet 2'70 restores itsinterrupter contacts 271 at the end of the first automatic rotary step,the busying ground from the second engaged busy trunk is extended to theEC wiper 293 as previously described for operating the rotary step relay260 over the previously traced circuit. Relay 260 operates and completesthe circuits as previously described to cause the rotary magnet 270' toadvance the connector wipers 2% through 293 to the next successive setof bank contacts which represent the third trunk of the group.

If it is assumed that this third trunk and the fourth, fifth, and sixthtrunks are all busy, the above-described interaction between the rotarystep relay 260 and the rotary magnet 270 will continue until the wipersare advanced to engage a set of bank contacts representing a trunk thatis idle, which in this case is assumed to be the seventh trunk.

At the time that the connector wipers engage the bank contacts that areconnected to the seventh trunk, the busy ground is no longer encounteredby the 'C Wiper 22 and EC wiper 2%, and battery potential, whichindicates an idle trunk, is encountered. This battery potential shuntsthe busy relay 220 so that this relay restores to open the circuit tothe rotary step relay 250. Since relay 250 does not operate over the ECconductor, rotary magnet 270 will not operate and slow-to-release relay259 will eventually restore to complete the previously traced energizingcircuit for operating switching relay 230.

From this point onward, the connector operates in the same manner asdescribed in the previous section entitled PBX call with First Trunk ofGroup Being Idle, wherein the signaling connection is extended to PBX 91by way of the seized seventh trunk and the talking connection isthereafter established.

At the end of conversation, the connector is restored in the same manneras previously described and conditioned to handle future calls.

9 Release Camping With All-Trunks-Busy A description will now be givenwherein it is assumed that all of the trunks in the trunk group assignedto PBX 01 are busy and that automatic trunk hunting takes placesubsequent to the group call number being dialed and in response to eachof these trunks in the group being tested and found busy.

In describing the operation of the connector during this type of call,it will be pointed out that the same operations have taken place as weredescribed in the previous sections wherein; the call was initiated atthe toll operators position and the toll connector was seized; the lasttwo digits ()1 of the call number were dialed to operate the connectorto engage its wipers with the first set of bank contacts in the tenth orlevel; and auto matic trunk hunting has taken place in the search for anidle trunk in the group, since it has been stated that all of the trunksin the group are assumed to be busy. In this description, the automatictrunk hunting takes place to successively test each busy trunk in thesame manner as previously described.

It will be pointed out at this time that the C and EC bank contactsrepresenting the last tmnk in the group are not connected together.Therefore, when all of the preceding trunks have been tested and foundbusy and when the connector wipers are advanced to engage the set ofbank contacts representing the last trunk of the group, the busyingground encountered by the C wiper 292 is not encountered by the EC wiper293.

At this point in the description it is also pointed out that when therotary magnet 270 operated to advance the wipers 290 to 293 intoengagement with the set of bank contacts representing the last trunk ofthe PBX group, the busying ground of this last trunk was encounteredonly by C wiper 292 for operating busy relay 2%, while the interruptersprings 271 of rotary magnet 27% then opened the circuit of rotary steprelay 260. Busy relay 22% operates and rotary step relay 260 restores tocause the various operations as previously described, namely wherein thevarious circuits are prepared by busy relay 226 and relay 26% opens itsholding circuit and both the holding circuit to relay 251E and theoperating circuit to rotary magnet 270.

Rotary magnet 2179 therefore restores and since there is no groundencountered by the EC wiper 2%, the closing of interrupter springs 271have no effect on rotary step relay 256 so that no further attempt ismade to ad Vance the connector wipers beyond the set of bank contactsrepresenting the last trunk of the group.

After a period of time, slow-to-release relay 250 restores and completesan obvious busy tone circuit to the calling operator at contacts 251,completes both an operating circuit for the release control relay 2% anda shunting circuit for relay 210 at contacts 252, closes contacts 255 inorder to provide a locking circuit for the busy relay 22$ before itsenergizing circuit is opened by contacts 254, performs no usual functionfor the present at contacts 253 and opens a point in the energizingcircuit to relay 26% at contacts 255.

The shunting circuit for relay 210 may be traced as extending fromground at contacts 252, contacts 222; and in one direction down to theright-hand side of the winding of relay 21th; and in the other directionover conductor 13, contacts 131, conductor 14 and contacts 211 to theleft-hand side of the winding of relay 210. The operating circuit forrelay 200 may be traced as extending from ground at contacts 252,contacts 2-22, conductor 13, contacts 131, conductor 14, contacts 211and through the winding of relay 2% to battery.

In actuating its contacts, relay 200 completes an obvious circuit foroperating the release magnet 280, which upon operating causes theconnector wipers 290 through 293 to restore to normal in a well-knownmanner.

When the connector wiper shaft restores to normal,

10 VON springs 5 open the holding circuit to relay 130, which thereuponrestores.

Upon restoring, relay completes a previously traced circuit foroperating changeover relay at contacts 133 and opens both the previouslytraced shunting circuit of relay 21d and the operating circuit of therelease control relay 200 at contacts 131. The restoring of relay 130has no effect upon the connector at the remainder of its contacts. Theopening of contacts 131 by relay 130 now allows relay 210 to operate inseries with the release control relay 200 over an obvious circuit.

In actuating its contacts, relay 210 opens another point in both theaforementioned shunting circuit to itself and an operating circuit torelay 200 at contacts 211, closes an alternate point in the rotarypulsing circuit at contacts 212 and opens a point in the circuit to therelease magnet 280 at contacts 213.

Changeover relay 140 operates over a previously described circuit fromthe toll C conductor to prepare the vertical pulsing circuit and toreoperate relay 130, also as previously described. In reoperating, relay1'30 has no effect on the circuits of the connector other than to lockthe changeover relays 14G operated by way of VON springs 6 and itscontacts 132.

At this point in the operational description, it will be noted that theconnector is now in the partial release camping condition and in thisstage, relays 110, 120, 130, 140, 200, 210, and 220 are operated. Theconnector will remain in this partial release camping condition until itis either released by the toll operator or until the toll operator againdials the last two digits of the PBX group call number. It will befurther noted that since the busy relay 22b is locked operated, busytone is continuously being sent to the toll operators position. It willbe appreciated that when the toll operator first received this busy toneafter the last two digits ()1 of the PBX group call number had beendialed, it was an indication to the operator that all trunks were busy.However, when the operator continues to receive this busy tone after thelapse of a short period of time it is then an indication that theconnector is in the partial release camping condition. The operator maynow leave the connection, as it is set up, in this busy condition andhandle other calls. This busy tone being transmitted back to the tolloperator can also serve to inform the operator when she returns to thisconnection that the connector is still camping.

When the operator returns to the camping connector she may again dialthe last two digits 01 of the call number to test as to whether or notthere is still an all trunk busy condition. When the digit 0 is dialed,relays 200, 210, and 220 remain operated since the connector wipers arebeing stepped in the vertical direction. However, when the rotary digit1 is dialed, relay 240 operates in series with rotary magnet 270 in thesame manner as previously described, since relay 210 has made thisrotary pulsing possible by means of its closed contacts 212.

At this stage of the operation, the connector again tests for an idletrunk in the same manner as previously described. If no idle trunks arefound at the time that the counter wipers engage the contactsrepresenting the last trunk of the group, the connector wipers will berestored and the connector will camp in the same manner as previouslydescribed. However, if an idle trunk is found, the connector will switchthrough to connect with this idle trunk in the same manner also aspreviously described, wherein relay 250 operates responsive to theabove-mentioned operation of relay 240 and causes relays 200, 210 and220 to restore, and since an idle trunk is found as mentioned, the busyrelay 220 will not reoperate.

It is thought advisable to point out at this time that while the partialrelease camping features of this connector have been disclosed as beingused with a PBX toll connector, it would be obvious to also incorporatethis I 1 partial camping feature in a connector providing local service,with little if any modifications thereto.

At the end of conversation, the connector is restored in the same manneras previously described and conditioned to handle future calls.

Having described my invention, what is considered new and desired tohave protected by Letters Patent will be pointed out in the appendedclaims.

What is claimed is:

1. In a telephone system, a two-motion multi-level connector switch, aset of wipers included in said switch, a plurality of groups of trunklines, each of said groups of trunk lines being connected to a differentone of said levels, said trunk lines accessible to said connector switchby means of said set of wipers, a preceding switch train having accessto said connector switch operated in response to the initiation of acalling connection thereover for including said switch in said callingconnection, means for directively operating said connector switch oversaid connection to move said wipers in one of said motions to select oneof said groups of trunk lines in one of said levels, means for furtherdirectively operating said connector switch over said connection to movesaid wipers in the other of said motions to engage the first trunk insaid selected group, busy testing means in said connector switch fortesting the busy condition of each trunk in said selected group, meansoperated in response to said first trunk testing busy by said busytesting means for automatically operating said connector switch to movesaid wipers in said other motion to successively hunt for an idle trunkin said selected group, means including wiper restoring means operatedin response to the last trunk in said selected group being engaged bysaid wipers and found busy for automatically restoring only said Wipersto normal, means for maintaining said connector switch in said callingconnection with said preceding switch train subsequent to restoration ofsaid Wipers to normal, and means including means operated in response tosaid restoration of said wipers to normal for preparing said connectorswitch for subsequent reoperation of said wipers in the sameabove-mentioned said two directive motions whereby the busy condition ofsaid trunks in said selected group is retested.

2. In a telephone system such as claimed in claim 1, including a sourceof busy tone, a normally incomplete circuit for applying said busy toneto said calling connection, and means operated in response to theoperation of said means including said Wiper restoring means forcompleting said lbusy tone circuit to apply said busy tone to saidconnection, both before said release of said wipers to normal andsubsequently thereafter.

3. In a telephone system, a two-motion multi-level connector switch, aset of wipers included in said connector switch, a plurality of groupsof trunk lines, each of said groups of said trunk lines being connectedto a different one of said levels, said trunk lines accessible to saidconnector switch by means of said set of wipers, a preceding switchtrain having access to said connector switch operated in response to theinitiation of a calling connection thereover for including said switchin said calling connection, means for directively operating saidconnector switch over said connection to move said wipers in one of saidmotions to one of said levels to select one of said groups of trunklines, means for further directively operating said switch over saidconnection to move said wipers in the other of said motions to engagethe first of said trunks in said selected group, busy testing means insaid connec tor switch for testing the busy condition of each trunk insaid selected group, means operated in response to said first trunktesting busy by said busy testing means for automatically operating saidconnector switch to move said wipers in said other motion tosuccessively hunt for an idle trunk in said selected group, a releasecontrol relay, means for operating said release control relay subsequentto the last trunk in said selected group being engaged by said wipersand found busy, a wiper release magnet, a normally incomplete operatingcircuit for said wiper release magnet, means operated in response tosaid operation of said release control relay for completing said circuitto operate said wiper release magnet, whereby only said wipers arerestored to normal, means for maintaining said connector switch in saidcalling connection with said preceding switch train subsequent to saidrestoration of said wipers to normal, and means including means operatedin response to said restoration of said wipers to normal for preparingsaid connector switch for subsequent reoperation of said wipers in thesame above-mentioned said two motions, whereby the busy condition ofsaid trunks in said group is retested.

4. In a telephone system having a two-motion multilevel connector switchincluding a connection from a toll operator over a toll switch train inresponse to said operator dialing the preliminary digits of a callnumber, a set of wipers included in said switch, a plurality of groupsof trunk lines, each of said groups of trunk lines being connected to adiiferent one of said levels, said trunk lines accessible to saidconnector switch by means of said set of wipers, each of said groups oftrunk lines being assigned a pair of individual digits for representingthe final digits of said call number, means for directively operatingsaid connector switch over said connection to move said wipers in one ofsaid motions to select one of said groups of trunk lines on one of saidlevels in accordance with the dialing of a first one of said finaldigits, means for directively operating said connector switch to movesaid wipers in the other of said motions to engage the first trunk insaid selected group in accordance with the dialing of a last one of saidfinal digits, busy testing means for testing the busy condition of eachtrunk in said selected group, means operated in response to said firsttrunk testing busy by said busy testing means for automaticallyoperating said connector switch to move said wipers in said other motionto successively hunt for an idle trunk in said selected group, meansoperated in response to the last tnmk in said selected group beingengaged by said wipers and found busy for restoring only said wipers tonormal, means for maintaining said connector switch in said callingconnection from said toll operator subsequent to said restoration ofsaid wipers to normal, motion preparing means including control meansoperated responsive to said restoration of said wipers to normal forpreparing said connector switch for the subsequent directive operationthereof to move said wipers in said one motion, relay means, anoperating circuit for said relay means, a shunting circuit normallyrendering said operating circuit ineffective, means operated responsiveto said operation of said motion preparing means for opening saidshunting circuit to thereby render said operating circuit efiective foroperating said relay means, and means operated in response to saidoperation of said relay means for preparing said connector switch forthe subsequent directive operation thereof to move said wipers in saidother motion.

5. In a telephone system, a plurality of groups of trunk lines, eachgroup of trunk lines being assigned a pair of individual digits forrepresenting the final digits of a call number, a connector switchhaving access to said trunk lines, an operators position, a precedingswitch train, means for establishing a connection from said operatorsposition to said connector switch over said switch train in accordancewith the dialing of the preliminary digits of said call number by saidoperator, means for operating said connector switch to select a group ofsaid trunk lines in accordance with the dialing of a first digit of acertain pair of said final digits in said call number, means forthereafter operating said connector switch to connect the first of saidtrunks in said selected group in accordance with the dialing of the lastdigit of said certain pair of said final digits in said call number,busy testing means for testing the busy condition of each trunk in saidselected group, means operated in response to said first trunk testingbusy by said busy testing means for automatically operating saidconnector switch to successively hunt for an idle trunk in said selectedgroup, release means in said connector switch, means for operating saidrelease means in response to the last trunk in said selected grouptesting busy 'by said ibusy testing means for causing said release meansto restore said connector switch from only said trunk selecting and saidtesting operations, means for maintaining said connector switch in saidestablished connection from said operators position over said switchtrain subsequent to said release, and means operated in response to saidrestoration for rendering said connector switch reoperative to thesubsequent redialing of said certain pair of said final digits toreselect said same group of trunk lines and reconnect with said firsttrunk in said reselected group, whereby said connector switch isautomatically reoperated to perform a second trunk hunting operation forretesting said trunks of said reselected group by said busy testingmeans.

6. In a telephone system, a connector switch, an operators position, aswitch train controlled by said operator, means for extending aconnection from said operators position over said switch train inaccordance with the dialing of the preliminary digits of a call numberto seize said connector switch, a first release means in said connectorswitch, means operated in response to said seizure for operating saidfirst release means, holding means for maintaining said first releasemeans operated under supervision of said operator-controlled switchtrain, means operated by said operation of said first release means forthereafter rendering said holding means eiiective, other meanscontrolled by said first release means for rendering said connectorswitch responsive to subsequent dialing operations, trunk lines arrangedin groups, each said group of trunk lines being assigned a pair ofindividual digits representing the final digits of said call number,wipers in said connector switch having access to said trunks, means fordirectively operating said connector switch toraise said wipers toselect one of said groups in accordance with the dialing of a firstdigit of a certain pair of said final digits, means for thereafterdirectively operating said connector switch to rotate said wipers toconnect with the first trunk in said selected group in accordance withthe dialing of the last digit of said certain pair of said final digits,busy testing means for testing the busy condition of each trunk in saidselected group, means operated in response to said first trunk testingbusy by said busy testing means for automatically operating saidconnector switch to rotate said wipers to successively hunt for an idletrunk in said selected group, a second release means in said connectorswitch, a first and a second operating circuit for said second releasemeans, means operated in response to the last trunk in said selectedgroup being tested and found busy by said busy testing means forcompleting said first operating circuit to operate said second releasemeans torestore only said wipers, means operated in response to saidrestoration of said wipers for rendering said connector switchreoperative to the subsequent redialing of said certain pair of saidfinal digits, whereby said same group of trunks is reselected and saidfirst trunk thereof is reconnected therewith, means responsive to saidfirst trunk being tested and found idle by said busy testing means forextending the said connection thcreover from said o-perators position,said holding means rendered ineffective over said operator controlledswitch train responsive tosaid extended connection being terminated atsaid opcrators position for restoring said first release means, wherebysaid connector switch is rendered unresponsive to subsequent dialingoperations, and means operated in response to said restoring of saidfirst release means for completing said second operating circuit tooperate said second release means to restore said wipers.

Beale et al. Aug. 13, 194-0 Molnar June 18, 1957

